326 Correspondence. 
CORRESPONDENCE. 
—+— 
THE OUTLIER OF CARBONIFEROUS LIMESTONE NEAR 
CORWEN. 
To the Editor of the GroLoGicAL MAGaziInr. 
Srr,—Pending the appearance of Professor Ramsay’s Memoir on 
North Wales, in which the conclusions arrived at by the Geological 
Survey will doubtless be fully stated, will you allow me briefly to 
give some of the reasons for believing that the outlier of Carboni- 
ferous Limestone near Corwen formed originally part of that which 
now sweeps round North Wales from Llany Mynech to the Great 
Orme’s Head? 
The country around Corwen was examined by Mr. Talbot Aveline 
and myself; who spent many pleasant but laborious months in it, so 
that not only was no rock-exposure unknown to us, but there was 
hardly a boulder with which one or other of us could not claim a 
personal acquaintance. If, therefore our conclusions are wrong (and 
I, for one, utterly abjure all pretension to infallibility), it is not that 
we spared our labour in examining the ground, and collecting data 
for arriving at them. 
The patch of Carboniferous Limestone at Hafod y Calch is on the 
downthrow side of the great ‘Yale and Bala’ fault which cuts 
across Merionethshire and Denbighshire from SW. to NE. On ~ 
examining the Survey section, sheet 39, it will be seen that the 
limestone dips to the NE., as mentioned by Mr. Davies,* and also 
that it rests unconformably on the Wenlock Shale, from beneath 
which the Tarannon Shale rises out, about 2 miles to the SW. On 
the SE. side of the fault the Tarannon Shale is at the surface close 
to Corwen, with the Wenlock Sbale (or Denbighshire Grits, which 
in all this region form the base of that shale) just over it. 
The rough diagrammatic section, fig. 1, will serve to give a general 
notion of the facts. 
Fig. 1. 
Carbonif. 
Limestone. 
Yale and 
Bala fault. 
oa 
os 
Caeran ac 
Crywni. Wenlock Shales. Hs Corwen. 
According to the section, there is a thickness of about 3,000 feet 
between the base of the limestone and the Tarannon Shale, which, 
* See Grorocican Magazine, Vol. II., p. 283. 
